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首页> 外文期刊>日本作物學會紀事 >Studies on Competition between Upland Crops and Weeds : IV. Change of light environment in crop canopies and hypothesis about the period for weed-free maintenance
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Studies on Competition between Upland Crops and Weeds : IV. Change of light environment in crop canopies and hypothesis about the period for weed-free maintenance

机译：高地作物与杂草竞争的研究：IV。作物檐篷和假设在无杂草维护时期的光环境变化

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The changes of light environment in crop canopies were investigated with four upland crops which were typical in the Kanto plain. And, the growth of competitive weeds was made clear clear, then we hypothesized about the period for weed-free maintenance after seeding required to escape crop yield reduction due to weeds. 1. The start of shading the surface of the ground by crop canopies after seeding was earliest in corn, but reduction of relative light intensity under crop was slow, and the degree of shading was small. The start of shading by soybean was a little late as compared with that of corn, but reduction of relative light intensity was rapid, and the degree of shading was large. The start of shading was the latest in peanut, but reduction of relative light intensity was the most rapid and the degree of shading was large as well as soybean. The characteristics of shading in upland rice were medium among these crops. 2. High negative correlation was found between logarithms of relative light intensity in the center of crop-rows on the surface of the ground and the number of days after seeding, then the regression lines were obtained. From these regression lines, the times when relative light intensity reduced under 20% were estimated, that is, about 76, 78, 63 and 71 days after seeding in upland rice, peanut, soybean and corn, respectively. And similarly, the times when reduced under 10%, were about 89, 86 and 73 days after seeding in upland rice, peanut and soybean, respectively. Reduction under 10% was not found in corn. 3. The linear regression was obtained between logarithms of relative light intensity in the center of crop-rows on the surface of the ground and LAI. From these regression lines, LAIs at the time when relative light intensity reduced under 20% or 10%, were estimated, that is, 4.9 or 6.6, 2.7 or 3.7, 2.3 or 3.3 and 5.2, in upland rice, peanut, soybean and corn, respectively. 4. At the time when relative light in the center of crop-rows on the surface of the ground reduced under 20% or 10%, the space of 40 or 30 cm-high from the surface of the ground in upland rice, 20 or 15 cm-high in peanut, 60 or 50 cm-high in soybean and 100 cm-high in corn kept the same value of relative light intensity, respectively. 5. In the early summer season when relative light intensitywas reduced by crop canopies, plant length or main stem length of weeds was 1-2, 7-13, 16-28, 39-52 cm in large crab-grass (Digitaria adscendens Henr.), 1-2, 6-12, 12-26, 20-43 cm in Chufa (Cyperus microiria Steud.), and 1, 4-14, 9-25, 17-33 cm in common purslane (Portulaca oleracea L.)at 10, 20, 30, 40 days after seeding, respectively. 6. From above results. we build up hypothesis about the period for weed-free maintenance after seeding required to escape crop yield reduction due to weeds, as follows. Growth of large crab-grass is greatly diminished at the condition of relative light intensity under 10%. The relative light intensity in crop canopies reduced under 10% at the time of about 89 days after seeding, and the space of 30 cm-high was the same value in upland rice. On the other hand, plant length of large crab-grass grew about 30 cm at the time of 30 days after weed seeding. Therefore, 59 days which went back from 89 days to 30 days were estimated as the period for weed-free maintenance, in the community of upland rice and large crab-grass. It was expected that the growth of large crab-grass which emerged on and after 59 days after crop seeding was greatly diminished by crop canopies. The relative light intensity did not reduce under 10% in corn, but from its characteristics, less than 30 days were estimated, as the period for weed-free maintenance. The period for weed-free maintenance were estimated shorter in common purslane or Chufa. Their growth are greatly diminished at the condition of relative light intensity under 20%.
机译：研究了作物檐篷中的光环境的变化，并用四个普通作物进行了典型的典型作物。而且，竞争性杂草的增长清晰明确，然后我们假设播种后无杂草维护的时期，以逃避由于杂草而逃避作物产量。 1.在玉米中，作物檐篷遮蔽地面的表面的开始，但在玉米中最早减少作物的相对光强度较慢，遮阳度小。与玉米相比，大豆的遮阳开始有点晚，但相对光强度的降低迅速，遮阳度大。着色的开始是最新的花生，但相对光强度的降低是最迅速的，阴影程度很大以及大豆。山地水稻遮阳的特征是这些作物中的中等。 2.在地面表面上的作物行中心的相对光强度的对数和接种后的天数之间的对轨肌之间发现了高负相关性，然后获得了回归线。从这些回归线，估计相对光强度降低的相对光强度减少的时间，即在旱稻，花生，大豆和玉米中播种后约76,78,63和71天。同样地，在旱稻，花生和大豆的播种后，减少10％的时间约为10％，约为89,86和73天。在玉米中未发现10％以下的减少。 3.在地面和赖的裁剪中心中心的相对光强度的对轨道之间获得线性回归。从这些回归线，估计相对光照强度降低的时间为20％或10％，即4.9或6.6,2.7或3.7,2.3或3.3和5.2，在Upland米，花生，大豆和玉米中， 分别。 4.在地面表面上的作物中的中心的相对光的相对光降低20％或10％，从旱稻的地面表面40或30 cm高的空间，20或花生15厘米高，大豆60或50厘米高，玉米中100厘米高，分别保持相同光强度的值。 5.在夏季初期的作物檐篷减少时，杂草的植物长度或主要茎长度为1-2,7-13,16-28,39-52厘米（Digitaria Adscendens Henr 。），1-2,6-12,12-26,20-43厘米在Chufa（Cypetus microiria steud）和1>，4-14,9-25,17-33cm，普通的追踪（portulaca oleracea L.）分别在播种后10,20,30,30,30天。 6.从上面的结果中。我们在播种后杂草维护的时期建立假设，以逃避由于杂草而减少的作物产量减少，如下所示。大螃蟹草的生长在10％以下的相对光强度的条件下大大减少。作物檐篷中的相对光强度在接种后约89天的时间下减少10％，并且30厘米高的空间在旱稻中具有相同的价值。另一方面，杂草播种后30天的植物长度长达30厘米。因此，从89天到30天后的59天估计是北方米饭和大型螃蟹草社区的无杂草维护的期间。预计在作物播种后59天内和59天后出现的大型蟹草的生长大大减少了作物檐篷。玉米中相对光强度没有减少10％，但从其特点估计，估计不到30天，作为无杂草维护的时期。杂草维护的时期估计普通的追踪或Chufa较短。它们的增长在相对光强度的情况下大大减少了20％。

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